Mass transport in metal-organic frameworks as a limiting step in size-selective oligomerization

Abstract

Metal organic frameworks (MOFs) are a relatively new class of crystalline, porous materials at the interface of organic and inorganic chemistry that have been applied in gas absorption and storage systems, thin-film devices, and heterogeneous catalysts. While numerous examples of size-exclusive catalysis have been reported, to our knowledge no reports of size-selective oligomerization catalysis have been reported to date. Herein, chemically stable Zr based MOFs, namely UiO-67 and PCN-777, are investigated as possible candidates to promote size-selective oligomerization catalysis. Using acylated propylene-glycol methyl ethers as model substrates, the mass transport properties of these materials was investigated. Unfortunately, slow mass transport of solvated substrates through pores assumed to be sufficiently large for facile diffusion may prevent MOFs from serving as suitable scaffolds. Indeed, pore apertures large enough for quick diffusion rates may require pore volumes too large to allow reasonable size-selectivity.